Hydrocarbon treating process



April 19, 1966 R. A. WooDLE HYDROCARBON TREATING PROCESS Filed May 28, 1964 United States Patent() 3,247,101 HYDROCARBON TREATING PROCESS Robert A. Woodle, Nederland, Tex., assgnor to Texaco Inc., New York, N.Y., a corporation of Delaware Filed May 28, 1964. Ser. No. 370,982 4 Claims. (Cl. 208-313) This application is a continuation-in-part of application Serial No. 124,839 tiled Iuly 18, 1961 now Patent 3,167,- 501.

This invention is directed to a hydrocarbon treating process. More particularly, it relates to a method of refining a hydrocarbon oil by liquid-liquid solvent extraction employing furfural as a solvent.

In accordance with the process of this invention, a hydrocarbon oil boiling within the range of about 250 to 600 F. is contacted with a solvent comprising furfural and containing at most about 0.5 Weight percent dissolved water, and furfural is separated from the resulting ratiinate and extract-mix phases by distillation in the absence of added steam. Separation of furfural from the raffinate is effected by an azeotropic distillation employing hydrocarbon separated from the hydrocarbon oil feed as an azeotrope former. Furfural is separated from the extract-mix by extractive distillation in the presence of a relatively high boiling hydrocarbon oil effecting separation of furfural distillate substantially free of hydrocarbon. Extractive distillation bottoms are stripped to separate extract and any remaining furfural from the heavy hydrocarbon oil which is returned to the extractive distillation tower. Extract stripped from the heavy hydrocarbon is separated from any remaining furfural by distillation in an azeotropic distillation zone employing hydrocarbon separated from saidextract as azeotrope former.

In solvent refining processes where @the solvent and material treated have substantially different boiling ranges, the solvent is readily separated from the extract and rafnate phases by simple distillation. However, separation by simple distillation is incomplete *when the oil treated contains components having true boiling points in the region of the boiling range of the solvent. In my co-pending application, Serial No. 124,839, tiled July 18, 1961 of which this application is a continuation-in-part, I have described a method of treating hydrocarbon stocks containing components co-boiling with the solvent employing azeotropic distillation with steam to separate solvent from the rainate and extractive distillation and steam stripping to separate solvent from the extract-mix. When the furfural solvent is separated by stripping or azeotroping with steam, the recovered solvent is satura-ted with water. (Furfural containing dissolved water in excess of about 0.5 weight percent is referred to hereinafter as wet.) When employing Wet furfural for extraction, the solubility of hydrocarbons is markedly reduced so that considerably higher solvent dosages and higher temperatures must be employed to obtain the same yields upon extraction. If high dosages are to be avoided, wet furfural must be subjected to further distillation for separation of the dissolved water. I have now found that the solvent may be separated from the extract-mix and from the raiiinate by distillation in the absence of added steam by employing a part ot the hydrocarbon feed stock as an azeotrope former. Furfural and hydrocarbon boiling within the range of about 200 to 430 F. form azeotropes with furfural. These azeotropes are lower boiling than either furfural or the specic hydrocarbon species present in the azeotrope and are het-erogenous, that is, upon condensation, they form separate hydrocarbon and furfural phases. The separated furfural phase may be returned to the extraction system and the separated hydrocarbon phase may be returned -to the azeotropic distillation to supply the entire ice requirement of azeotrope former. In this way furfural is separated free of water and at the same time, the hydrocarbon product is effectively stripped of furfural.

It is an object of this invention to provide a means of treating hydrocarbons boiling within the range of about 250 to 600 F. and containing a substantial portion of hydrocarbons boiling less than 430 F. with furfural as a solvent. It is a further objective of this invention to provide a means of treating such hydrocarbons with furfural and distillatively separa-ting the furfural from the resulting extract-mix and the raihnate by distillation in the absence of steam whereby the furfural is separated in the substantial absence of dissolved water. An advantage of the process of this invention is that the solvency of the furfural is maintained at a high level whereby the solvent dosage may be maintained at a reasonably low level. Other objects and advantages will be apparent from the following description and claims.

In the solvent extraction step of this process, the principal variables in the process are: charge stock boiling range, extraction temperature, and solvent dosage. Since the. solvent removal from both the refined oil and extract oil ultimately depend upon formation of binary hydrocarbon-furfural azeotopes from the hydrocarbons present in the feed stock itself, it is important that the charge stock have an initial boiling point of at least 200 F., and preferably of at least 250 F. to exlude lower-boiling nonazeotroping hydrocarbons. The charge stock boiling range should -be limited to an end point of about 600 F. to insure easy separatori from the heavy parainic oil used as extractive distillation solvent. Extraction temperatures are limited to temperatures below the miscibility point for the particular solvent dosage being used. Preferred temperatures are in the range from F. to 170 F. Preferred solvent dosages are in the range from 50 to 350 volume percent basis charge oil. In the azeotropic distillation of the raiIinate-inix, the principal feature of this invention is that the azeotrope former is a portion of the hydrocarbon feed and the amount of azeotrope former required is supplied by recycling separated distillate in a quantity sucient to satisfy the requirements for the azeotrope former. By returning all of the hydrocarbon separated as distillate to the distillation zone, the entire requirement oi hydrocarbon to strip all of the furfural out of the raflinate is obtained. This hydrocarbon is returned to the distillation tower as reux and t-hedistillation can therefore be operated with no net hydrocarbon distillate production and all of the rened oil stripped of furfural is withdrawn as bottoms from the azeotropic distillation tower.

In the extractive distillation step of this invention, distill'ative separation of solvent from dissolved hydrocarbon is effected in the presence of a relatively rhigh-boiling hydrocarbon oil. The presence of the high-boiling oil reduces the relative volatility of the co-boiling components of the dissolved oil so that solvent free of co-boiling hydrocarbons is removed as distillate and all of the oil initially dissolved in the solvent is removed as bottoms with the relatively high-boiling oil. The extractive distillation is effected at a pressure selected to augment the elfect of the high-boiling oil on the relative volatility of the coboiling hydrocarbon and to achieve optimum and most economical equipment design and operation. Preferred pressures in they extractive distillation step may be within the range of less than atmospheric, that is, a vacuum, up to about five atmospheres or higher. The relatively highboiling oil itself should be free of components boiling in the region of the solvent and preferably should consist of components having true boiling points at least F. above the boiling range of the solvent. Additionally the high-boiling oil should consist of components boiling wholly above the treated oil. When Vtreating oil boiling 3 within the range `of250 to 600 F., with dry furfural which boils at 323 F., it is preferred to employ a parainic`oil boiling wholly 'aboutl70'0 F2 at atmospheric pressure. Suitable high-boiling oils include both distillates and residual oils. In the extractive distillation step, it is frequently advantageous to separate a major portion of the furtural as distillate leaving a minor portion of the furfural in the bottoms to prevent carryover of the oil being treated. In this case, the furfural is removed as distillate when stripping the extract from the. heavy oil. The furfural then is separated from the extract by a further distillation employing the oil constituents as azeotrope formers so that this furfur-al is also separated ,in the labsence of added water;

The accompanying drawing diagrammatically illustrates one embodimentl of the process of this invention. Although the drawing illustrates an arrangement of apparatus in which the process of this invention may be practiced, it is not intended to limit the invention to the particular apparatus or materials described.

Referring to the ligure, a hydrocarbon stock consisting predominantly of hydrocarbons boiling in the range of 250 to ,600 F. is .charged through line 1 to extraction tower 2. In extraction tower 2, the oil is countercurrently 4contacted with solvent introduced into the top of tower 2, through line 3. Rainate-mix, comprising refined oil and a small amount of dissolved solvent, is withdrawn through line 4 and passed to distillation column 7. Since the refined oil itself is comprised largely of hydrocarbons which form binary azeotropes with furfural, the overhead vapor from column 7 consists of azeotropes of furfural with hydrocarbons occurring naturally in the extraction charge stock, thereby removing all of the solvent in the azeotropic mixture withdrawn as distillate through line 10. Refined oil free of solvent is withdrawn from the bottom of tower 7 through line 11.

f The azeotropic mixture comprises vapors of solvent and a small amount of hydrocarbon oil. The vapor mixture iscondensed in cooler and the resulting condensate is passed through line 16 to separator 17. Two liquid phases separate, that is an oil phase (lighter) containing a small amount of dissolved solvent and a solvent phase (heavier) containing a small amount of dissolved oil. Separated solvent phase is withdrawn through line 20 and returned to extraction tower 2 through line 3. Separated oil phase is withdrawn through line 22 and is returned, at least in part, to tower 7 as additional azeotrope-forming reux.

Extract-mix is withdrawn from extraction tower 2 through line 32, heated in heater 46 and passed through line 49 to extractive distillation tower 50.

In extractive distillation tower 50, the hydrocarbon and solvent vapors are distilled in contact with a relatively high boiling hydrocarbon oil introduced into the top of tower 50 through line 55. By distilling the solvent and extract vapors in contact with the high-boiling oil, the extract vapors are condensed in the high-boiling oil and solvent essentially free of oil is removed as' distillate through line 56, condensed in cooler 23 and run to solvent storage drum 25 through line 24. The extractive distillation tower bottoms, comprising the high-boiling oil, extract oil, and a part of the solvent, are withdrawn through line 57 and passed through heater 58 and line 59 to extract stripping tower 60.

'In extract stripping tower 60, essentially all of the solvent contained in the heavy oil is distilled overhead as a binary azeotrope along with the extract oil. High-boiling oil is withdrawn from the bottom of tower 60 for recycle to extractive distillation tower 50 through line 55. Extract and solvent vapors removed as distillate from tower 60 are passed through line 65, cooler 66, and line 67 to separator 68. In separator 68, two liquid phases are formed. A heavier solvent phase comprising the solvent plus a small amount of dissolved oil is withdrawn through line 76 and is returned to the extract-mix line 32. A lighter oil phase comprising the extract oil plus a small Y 72 and passed through heater 73 into azeotropicrdistilf lation tower 80. y

Since the extract oil itselfis comprised largely of hydrocarbons which form binary azeotropes with furfural, the overhead vapor from column consists of azeotropes of furfural with hydrocarbons occurring naturally in the extraction charge stock. All of the solvent charged to column 80 is withdrawn `with the distillate as an azeotropic mixture, through line 81. Extract oil free of solvent is withdrawn from the bottom of tower 80 through line 82.

The azeotropic mixture comprises vapors of solvent and a small amount of hydrocarbon oil. The vapor mixture is condensed in cooler and the resulting condensate is passed through line 91 to separator 92. Two liquid phases separate, that is an oil phase (lighter) containing a small amount of dissolved solvent and a solvent phase (heavier) containing a small amount Aof dissolvedv oil. Separated solvent phase is withdrawn through line 93 and returned to the extract-mix line 32. Separated oil phase is withdrawn through line 94 and is returned to column 80 as additional azeotrope-forming reilux.

Example I The following example illustrates the application of the process of this invention to the refining of a kero-V sene stock useful in the manufacture of jet fuel. In the following example, ow rates are expressed in terms of liquid barrels per hour regardless of whether the particular stream is in the liquid or vapor form. v

A kerosene stock having an ASTM distillation initial 4boiling point of 316 F.,4 a 50 percent point of 407 F., and an endpoint of 502 F. at a rate of l0 barrels per hour is countercurrently contacted with 14.8 barrels per hour of solvent having a composition of 94.2 percent furfural, 5.8 percent dissolved oil and less than 0.1 percent dissolved water. Extraction is eifected with a top tower temperature of F. and a bottoms tower temperature of F. Rainate mix at a rate of 8.8 barrels per hour is distilled at a top tower temperature of 348 F. to produce 8.2 barrels per hour of oil bottoms free of solvent and an overhead azeotropic distillate. The azeotropic-distillate is condensed separating 0.6 barrels per hour of solvent phase comprising 93 percent furfural and 6 percent toil, and 1.2.9 barrels per hour of oil phase comprising 93 percent oil and 7 percent furfural. The solvent phase is returned as part of the solvent passed to the extraction tower. The oil phase is returned as reflux to the raffinate mix fractionator.

Extract-mix at a rate of 16.0 barrels per hour comprising 83 percent furfural and 17 percent oil together with 0.2 barrels of recovered solvent as hereinafter provided comprising 93 percent furfural and 7 percent oil is heated to 325 F. and passed to anextractive distillation tower operated at 9 p.s.i.g. and a top tower temperature of 351 F. A heavy paraiin-ic distillate oil boiling wholly above 760 F. at-.atmospheric pressure is reiluxed to the top of the extractive distillation tower at a rate of 26.6 barrels per hour. Extractive distillation tower overhead at a rate of 14.2 barrels per hour comprising 94.2 percent -furfural and 5.8percent oil is condensed and passed to a solventfsupply tank.

Extractive distillation tower bottoms, at a rate of 28.6 barrels per hour comprising 93 percent heavy oil, 0.7 percent furfural and 6.3 percent extract oil is heated to 600 F. and passed to an extractive solvent stripper, to recover 26.6 barrels per hour of heavy oil as bottoms for recycle to the extractive distillation tower and 2.0 barrels per hour o fdis'tillate. Distillate is condensed to form an oil phase comprising 90 percent extract oil and 10 percent f urfural.

Distillate from lthe extractive distillation is charged at a rate of 2.0 barrels per hour to an extract oil azeotropic distillation tower at a pressure of 10 p.s.i.g. and a top tower temperature of 329 F. to produce 1.8 barrels per hour of furfural free bottoms and 2.20 barrels per hour of distillate. This distillate is condensed and separated into a heavy furfural phase comprising 93 percent furfural and 7 percent oil, and a lighter oil phase comprising 93 pencent -oil and 7 percent furfural. The oil phase is returned to the azeotropic tower as reflux. The solvent layer is returned to the extract-mix stream leaving the extractor.

A comparison of tests on the charge kerosene and on the refined kerosene from the operation as described above is shown in Table I:

The results demonstrate the effectiveness of the process for removing aromatics and improving the smoke point, luminometer number, and dinuclear aromatics values.

Example Il In another example of the process of this invention, a catalytically cracked light cycle gas oil is refined reducing the aromatic content and carbon residue. For comparison, the same oil is refined by an analogous procedure except that the furfural is separated from the resulting raffinate and extract-mix phases by steam stripping and contains about 5.0 weight percent water. The results of this comparison are shown 1n Table II.

TABLE II Furfural Furfural stripped stripped with hydrowith steam carbon azeotrope Charge Stock Tests:

RI at 70 C 1. 4890 Gravity, API 27. 2 Carbon Residue, 10% bottoms, Wt. Percent. 0. 48 Aromatics, Vol. Percent 55. 9 ASTM Distillation, F.-

Rates, cc./hr.:

Charge Oil 7, 522 9,850 Furfur 15, 060 10, 400 Solvent Dosage, Vol. Percent 200 106 Water Content of furfural, Wt. Percent. 5. 0. 5 Temperatures, F.:

Rafiinate outlet 119 120 Extract-mix outlet 94 92 Oil in Extract-mix, Vol. Percent 20. 5 39.0 Yield o Refined Oil, Vol. Percent 54. 6 67, 3 Refined Oil Tests:

RI at 70 C 1. 4395 1. 4387 Gravity, API." 40. 5 41. 8 Color, ASTM less than less than 2. 0 1. 5 Sulfur E 1 0. 07 0. 05 Carbon Residue Bottoms W er- Ceut 0. 09 o. 07 Aromatics, Vol. Percent 20. 8 17` 3 It will be noted from the above comparison that dry furfural (containing 0.5 weight percent dissolved water) at comparable extraction temperatures produces an appreciably higher yield of somewhat superior refined oil and with a solvent dosage of only about half that needed using wet furfural. The higher oil content of the extractmix with dry solvent, 39.0 as compared with 20.5, shows the superior oil-carrying power of dry furfural over wet furfural.

I claim:

1. In the solvent refining of a hydrocarbon oil boiling within the range of about 250 to 600 F. and having an ASTM distillation 50 percent point less than 430 F. wherein said hydrocarbon oil is contacted with a solvent comprising furfural forming rafiinate and extract-mix phases and refined oil and extract are separated from said railinate and extract-mix phases respectively, the improvement which comprises:

contacting said hydrocarbon oil with a solvent consisting essentially of furfural and containing at most about 0.5 weight percent dissolved water forming raffinate and extract-mix phases,

separating said phases, distilling said raffinate phase in the presence of a hydrocarbon azeotrope former separated from said raffinate and in the absence of added steam in a distillation zone separating an azeotrope of furfural and hydrocarbon as distillation vapors from refined oil as distillation bottoms,

condensing said distillation vapors forming a hydrocarbon phase and a furfural phase, and

passing at least a part of said hydrocarbon phase to said distillation zone as said hydrocarbon azeotrope former.

2. In the solvent refining of a hydrocarbon oil boiling within the range of about 250 to 600 F. and having an ASTM distillation 50 percent point less than 430 F. wherein said hydrocarbon oil is contacted with a solvent comprising furfural forming raffinate and extract-mix phases and refined oil and extract are separated from said raiiinate and extract-mix phases respectively, the improvement which comprises:

contacting said hydrocarbon oil with a solvent consisting essentially of furfural and containing at most about 0.5 weight percent dissolved water forming raffinate and extract-mix phases,

separating said phases, distilling said raffinate phase in the presence of a hydrocarbon azeotrope former separated from said raffinate and in the absence of added steam in a first distillation zone separating an azeotrope or furfural and hydrocarbon as distillation vapors from refined oil as distillation bottoms,

condensing said distillation vapors forming a hydrocarbon phase and a furfural phase,

passing at least a part of said hydrocarbon phase to said first distillation zone as said hydrocarbon azeotrope former,

distilling said extract-mix phase in the presence of an added high boiling oil having an ASTM initial boiling point of at least 625 F. and in the absence of added steam in a second distillation zone separating furfural substantially free of oil as distillation vapors from distillation bottoms comprising said high boiling oil and extract hydrocarbons, and

distilling said distillation bottoms from said second distillation zone in the absence of steam in a third distillation zone separating sai-d extract as distillate from said high boiling oil.

3. The process of claim 2 wherein the distillate from said third distillation zone comprises extract hydrocarbons and furfural and said extract and furfural are separated by an azeotropic distillation in a fourth distillation zone.

4. The process of claim 3 wherein the azeotropic distillation in said fourth distillation zone is effected in the presence of a hydrocarbon azeotrope former separated from said extract.

References Cited by the Examiner UNITED STATES PATENTS 2,070,384 2/1937 Tuttle 208--323 2,773,006 12/1956 Carver et al. 208-312 3,132,093 5/1964 Arnold et al. 208-327 DELBERT E. GANTZ, Primary Examiner.

HERBERT LEVINE, Examiner. 

2. IN THE SOLVENT REFINING OF A HYDROCARBON OIL BOILING WITHIN THE RANGE OF ABOUT 250 TO 600*F. AND HAVING AN ASTM DISTILLATION 50 PERCENT POINT LESS THAN 430*F. WHEREIN SAID HYDROCARBON OIL IS CONTACTED WITH A SOLVENT COMPRISING FURFURAL FORMING RAFFINATE AND EXTRACT-MIXPHASES AND REFINED OIL AND EXTRACT ARE SEPARATED FROM SAID RAFFINATE AND EXTRACT-MIX PHASES RESPECTIVELY, THE IMPROVEMENT WHICH COMPRISES: CONTACTING SAID HYDROCARBON OIL WITH A SOLVENT CONSISTING ESSENTIALLY OF FURFURAL AND CONTAINING AT MOST ABOUT 0.5 WEIGHT PERCENT DISSOLVED WATER FORMING RAFFINATE AND EXTRACT-MIX PHASES, SEPARATING SAID PHASES, DISTILLING SAID RAFFINATE PHASE IN THE PRESENCE OF A HYDROCARBON AZEOTROPE FORMER SEPARATED FROM SAID RAFFINATE AND IN THE ABSENCE OF ADDED STEAM IN A FIRST DISTILLATION ZONE SEPARATING AND AZEOTROPE OR FURFURAL AND HYDROCARBON AS DISTILLATION VAPORS FROM REFINED OIL AS DISTILLATION BOTTOMS, CONDENSING SAID DISTILLATION VAPORS FORMING A HYDROCARBON PHASE AND A FURFURAL PHASE, 